1. Field of the Invention
The present invention relates generally to power conversion circuits and more particularly to a boost converter that uses two pulse frequency modulation (PFM) operating modes for efficiency.
2. Description of the Related Art
Inductor based boost mode light emitting diode (LED) drivers typically include pulse width modulation (PWM) converters that operate at a fixed frequency. A PWM converter uses an oscillator to generate the fixed (or PWM reference) frequency and varies the switching duty cycle applied to a semiconductor switch to regulate an output voltage. The PWM converter can operate in a voltage mode or a current mode. In a current mode PWM converter, the output voltage is regulated indirectly by controlling a peak or an average switch current. In a voltage mode PWM converter, the output voltage is directly regulated. Both modes of operation can promote inefficiency (e.g., switching loss or conduction loss) as load current changes.